Ammonia-soda process for the production of sodium hydroxide, naoh, with simultaneousproduction of ammonia



Sept. 13, 1932. BARTLING 1,877,489

AMMONIA SODA PROCESS FOR THE PRODUCTION OF SODIUM HYDROXIDE, NEOH, WITH SIMULTANEOUS PRODUCTION OF AMMONIA Filed March 6, 1950 i II V pull q mum Patented Sept. 13, 1932 FRIEDRICH. BARTLING, or" HUGLFING, GERMANY mommsonx PROCESS ron'rrrn' rnonnorr'ononfsommvr HYDROXIDE; Neon, ,wrrn

' SIMULTANEO'USPRODUCTION'OF:AMMONIA' 1 Application filed March: 6," 1930; Serial' No.

The'inventionconsists in amodification of the; well. known ammonia-soda process for the production: of sodi'umhydroxide, which hasforits.- object theadditional production of; considerable quantities of ammonia and, by-ione method of application, of ammonium, chloride, without; material increase of the. operating. expenses. a

In general, in the alkali industry, two dif m ferent-industrial products areinanufactured by the ammonia-soda process, namely sodi-- um carbonate NagCOg; andsodium hydroxide (caustic soda), NaOH. 7 I

, The production of sodium carbonate. as a product intended for direct sale is ofno interest-inirelation to the present invention and zneed not, therefore,be further referred to. The operation of the process ofproduction I of sodium hydroxi de, hitherto known, will= first be describedwvith the aid ofthe diagrammatic representation of theiin stallation, shown in Fig. l; I, i V

As is well known, an intermediate product, sodium bicarbonate, NaHCO is first. precipitated by passing carbon dioxide into. an ammoniacal sodium chloride solution in the precipitating vessel 1a: i i

The charge of the bicarbonate precipitate ing vessel: 1a, after the NaI-ICO hasbeen precipitated, is conveyed to a.filter2a for-the purpose ofseparatingihesolid sodium bicarbonate:- After filtrationthe remaining aminonium chlorides olution isconveyed to the distilling. column -3a for the recovery ofthe" ammonia. i i V The ammonia liberated in the column is led to a receiver 4,from which it is conveyed further, as required, into the salt solution tankia for the productionof' further ammo niacal salt solution forfithe precipitation process in the tank 1a. t V

The sodium bicarbonate, collectedon' the filter 2a, is cOnveyedtoa solution tank 5a in which carbon-dioxide isdriven offi. by steam and the bicarbonate is converted'intoi a solution ofNa COa Thislatter is then conveyed to the oausticizing tan k'6a', in which,

it"is rendered caustic by the: addition: of-

quick-lime'; Afterthecompletion :ofrthecaus+ ticizing process; the; lye is" conveyed to the 433,700, and in Germany March 26, 7 1929;

settling tank 7a,- from whichit is conveyed for evaporation to the evaporating installation- 8a,1 which usually consists of several ev-aporators; From the evaporating instal-- lation the product passes to the melting-pot 9a; After; complete concentration the liquid causticsoda is filled into'iron drums at lOa', in which it solidifies and is then ready? for despatch' f V e i Now, according to-thepresent-invention, the above-described ammonia-soda process for the production-of caustic soda, NaOI-Lis in the first case so modified'thatamnmnia, NH is obtained inaddition. v I

For this purpose, "inthe new process, the causticizing; process, that is, the} conversion; of the: sodium bicarbonate, NaHCO into sodium hydroxide, NaOH, is effected in a novel and more advantageous, manner, .where-' by a considerably greater economic benefit is achieved than is attained by the method- 0f causticizingusually employed in theammo-, niaz-soda process; I 1 i invention consistsof a modifiedfammoniasoda" process for the: pIOd11Ct1OIlr0f caustlc soda, in which I NH}, vis simultaneously recovformedinto'caustic soda and ammonia at-a, f lower temperature (approximately 400 500? -by theaction ofsteam.

As is known, sodium bicarbonate is: convertedinto sodium carbonate in thei Thelen" pan at a temperature lying between 300, and; 400 0. i

The I action of the Thelenpan, thatis, the decomposition-r of'sodiumjbicarbonate, is re placed-in the new. causticizing(process by that of-the apparatus 7 inwhich the mixture In' accordance with this obj ect, the present for a suflicient length of-time to a high tem- NaHCO and carbon will be used as of sodium bicarbonate and carbon is treated with nitrogen.

As is already known, the fixation of nitrogen takes place at temperatures which are higher than those required for the conversion of sodium bicarbonate, NaHCO into sodium carbonate, Na CO The action of the nitrogen on the mixture therefore only commences when, as in the bonate, NaHCO into sodium carbonate Naioog, in the apparatus for theproduction of sodium cyanide is already complete, as obviously the mixture, which enters the apparatus when cold, must'have been subjected to the lower temerature at which sodium bicarbonate NaHCO is convertedinto sodium carbonate Na CO before it attains the tem perature at which nitrogen fixation commences. l 7

Therefore, in operatingthe new process, calcination in a special apparatus will usually be avoided during the causticizing process and a mixture of sodium bicarbonate, the raw material for such process.

' Thus the process is simplified by the direct use of sodium bicarbonate. i 7

As the conversion of sodium bicarbonate, NaHCO into Na CO has already occurred before the fixation of nitrogen, thisfl-further reaction occurs according to the following equation v v a l I .Na Co +4C+N 2NaCN+3CO When the-reaction according to the above equation has proceeded'to'a suificient extent, that is, when the mixture has-been submitted perature (for example, 1000C.), and to the action of nitrogen, the sodium cyanide is cooled to a temperature lying between 400 (J- a and 500C. and exp'osed'to the action of steam at thattemperature. V

. Caustic soda and ammonia are formed, as

shown by the following equation NaCN +2H O=NaOH+ co+N1-1,

a The caustic soda obtained according to the above equation is dissolved, the solution purified by filtration, decantation or any other suitable process and then evaporated, thatis,

treated in exactly the. same manner as the caustic soda lye produced by the ordinary ammonia-soda process. v The carbon, which is usually added in the form of coke, is recovered as carbon monoxide,

this gas can be advantageously utilized as a fuel gas.

The carbon dioxide, CO which is evolved during the conversionof sodium bicarbonate,

NaHCO into sodium carbonate,Na CO can be used, for example, forthe precipita- CO. Inthe process of alkali manufacture tion of sodium bicarbonate from the ammoniacal sodium chloride solution.

The only increased costs for raw materials entailed in the conversion of sodium bicarbonate, NaHCO into sodium hydroxide NaOH by, the new process are those of the introductionof nitrogen. This nitrogen can be cheaply obtained by any known process, for example, by the Linde process. Thelen pan, the conversion of sodiuni'bicar- For this reason the ammonia obtained as a second product is extremely cheap, whilst the costs of manufacture of the caustic soda are tained by the new process into the ammonia soda process in such a manner that this ad ditionally recovered ammonia is usedto replace'the ammoma preclpitated from the ammonium chloride solution in the form of solid ammonium chloride. An example of a method of arrangemen of an installation for carrying out the new process is shown diagrammatically in Fig. 2; The apparatus 1?) and 2?) correspond in their construction and purpose to those of an installation of the known type, as in Fig. l.

The apparatus 5?) and 6b serve for the con- ;version of the sodium bicarbonate into'causti'c soda, as'do the apparatus 5a and Gain the plant according to Fig. 1. f

The actual causticizing process is however, entirely different from that of the ordinary ammonia-soda process.

In this 7 case the sodium bicarbonate,

NaI-ICO precipitatedin solid form in apparatus 1b and 2b, is mixed with carbon (usually in the form of coke) and then introduced into the apparatus 5?), in which the mixture is exposed to the action of a current of nitrogen at a high temperature, for exampleat1O00FC. I

' By this means the sodium bicarbonate NaHCO which is introduced, is converted I intov sodium cyanide, NaCN. This sodium cyanide is then conveyed to an apparatus 612,

in which it istreated with steam at a lower temperature, whichmay, for example, lie between 400 C. and 500 C. I I, The sodium cyanide is thus converted into caustic soda, NaOH, and ammonia, NH

The same purposes as are served by the bicarbonate solution tank ajand causticizing tank 60 in the process according to Fig. 1 are served by the apparatus 5?)- and 6b in the modified process, in which the above-described chemical processes occur, and 'in.

which the sodium bicarbonate NaHCO 1 causticized with simultaneous new formation of additional ammonia NH From the apparatus 6?) the generated caustic soda is conveyed to the tank 7?), in which it is dissolved and purified by filtration or by any other process.

The caustic soda lye is then conveyed to the evaporating installation 8?) and 9b in which.

known process.

The production of ammonia in the new causticlzing process enables the whole ammonia-soda process to be carried out more economically in an especially easy manner.-

This can be effected, as shown in Fig. 2 and described earlier in this specification, by dispensing with the decomposition in the distilling plant, with the object of recovering the ammonia, of the ammonium chloride solution which is recovered from the process of precipitating sodium bicarbonate, NaI-ICO and instead thereof by separating ammonium chloride, NI-LGl, from the ammonium chloride solution in solid form by any known process and re-introducing into the ammonia-soda process the ammonia which is produced by the new caustizing process, thus replacing the ammonia which is precipitated in the form of ammonium chloride.

The re-introduction is effected, according to Fig. 2, thereby that the ammonia, NH produced during the ca-usticizing process, is directly added to the tank 36 in which solid ammonium chloride is precipitated.

The additionally added ammonia serves not only, as already mentioned, to replace the NH removed from the process of alkali manufacture in the form of solid ammonium chloride, but also renders possible a satisfactory precipitation of the solid ammonium chloride itself.

According to a process which is itself already lrnown, solid ammonium chloride can be separated very simply by re-saturating the ammonium chloride liquor with ammonia, then adding further sodium chloride and carbon dioxide to a certain degree of partial saturation and finally cooling the liquid to approximately 5 C.

On cooling under such conditions, solid ammonium chloride is precipitated.

The whole contents of the precipitation tank 35, after precipitation is complete, are conveyed to the filtering tank 4?) for the sepaation' of theprecipitated, solid ammonium chloride. r F The liquor obtained from this filter, which as already-explained, has been saturatedjwitl'i ammonia, sodium chloride and some carbon i dioxide in'the precipitating tank 3band fun therr'replenishedi in the same tankwith the full complement of chemicals for. a new precipitation of sodium: bicarbonate, is then fully prepared for the renewed precipitationfiof the bicarbonate and can therefore be conveyed: directly from the filtering tank to'the sodium: bicarbonate precipitation tank in. readiness for a further precipitation of sodium bicarbonate. 1 I V From. the preceding description the tech nical advanceachievedby the new methodof operation and theconsequent greatly cheapenedproduction 'ofthe two new by-products of" the caustic soda produced-by the ammonia-soda process, namely, ammonia, NHg, and ammonium chloride," (NILCL) will be obvious. Moreover, as has been shown, the whole manufacture constitutes a closed cycle of raw materials and manufactured products; Compared withthe ammonia-soda process for the manufactureoflsodium hydroxide,- "as hitherto used and as described earlier in this description for comparison, the modification of a portion of the complete process involves no serious extension of the required series of operations. On the other hand, an exceedingly important improvement of the economic result of the complete ammonia-soda process for the product-ion of caustic soda,

NaOH, is thus efl'ected by means of which several valuable, salable products are simultaneously produced extremely cheaply, in consequence of the modifications constituting the present invention.

I claim:

1. The method of producing ammonium chloride and sodium hydroxide comprising introducing carbon dioxide into a solution containing sodium chloride and ammonia,

whereby-sodium bicarbonate is precipitated and ammonium chloride is obtained in solution, treating the precipitated sodium bicarbonate in the presence of carbon with nitrogen at an elevated temperature, whereby ing the evolved ammonia to the ammonium chloride solution, whereby the latter compound is obtained in solid form.

2. The method of producing ammonium chloride and sodium hydroxide comprising introducing carbon dioxide into a solution containing sodium chlorideand ammonia, whereby sodium blcarbonate is precipitated and ammonium chloride is obtained in solution, treating the precipitated sodium bicar bonate in the presence of carbon with nitrotea gene at an elevated temperature,whereby sodium cyanide is produced, reacting the sald sodium cyanide with steam at a temperature between 400 and 500 C., whereby ammonia and sodium hydroxide are produced and returning the evolved ammonia to the ammonium chloride solution, whereby the latter compound is obtained in solid form.

3. The method of producing ammonium chloride and sodium hydroxide comprising introducing carbon dioxide into a solution containing sodium chloride and ammonia, whereby sodium bicarbonate is precipitated and ammonium chloride is obtained in solution, treating the precipitated sodium bicarbonate in the presence of carbon with nitrogen at a temperature of about 1,000 0., whereby sodium cyanide is produced, reacting the said sodium cyanide with steam at a temperature between 400 and 500 (1, whereby ammonia and sodium hydroxide are produced, and returning the evolved ammonia to the ammonium chloride solution, whereby the latter compound is obtained in solid form. y

In testimony whereof I have signed my name to this specification.

' FRIEDRICH BARTLING. 

